White pulp compartments in the spleen of the turtle Mauremys caspica

Summary The aim of the present study was to analyze the nature of lymphoid and non-lymphoid cellular components occurring in distinct histological compartments of the splenic white pulp of the turtle, Mauremys caspica, in order to define their possible correlations with those of the spleen of higher vertebrates, principally mammals. The white pulp of M.caspica consisted of 3 clearly distinguishable regions: (1) the periateriolar lymphoid sheath, and (2) the inner and (3) the outer zones of the periellipsoidal lymphoid sheath. Reticular cells intimately associated with reticular fibres constituted an extensive meshwork in the periarteriolar lymphoid sheath which housed principally Ig-negative lyphoid cells, mature and immature plasma cells, and interdigitating cells. A few Ig-positive cells were also present in the peripheral region of the periarteriolar lymphoid sheath. The inner and outer zones of the periellipsoidal lymphoid sheath were separated by a discontinuous layer of reticular cell processes. In the inner zone, surface Ig-positive lymphoid cells predominated as well as dendritic cells, resembling ultrastructurally the mammalian follicular dendritic cells, although no germinal centres were found in the turtle spleen. Macrophages, some cytoplasmic Ig-positive cells, and Ig-negative lymphoid cells appeared in the outer zone of the periellipsoidal lymphoid sheath. These results allow us to speculate on a phylogenetic relationship between the periarteriolar lymphoid sheath and the inner and the outer zones of the periellipsoidal lymphoid sheath of the spleen of M. caspica and the periarteriolar lymphoid tissue, the lymphoid follicles and the marginal zone, respectively, of the mammalian splenic white pulp.     

Interdigitating cells in the thymus of the turtle Mauremys caspica

Summary Interdigitating cells are non-lymphoid elements in the thymus and peripheral, secondary lymphoid organs of higher vertebrates. Their origin and functional significance are a matter of controversy. In the present investigation we analyze, for the first time, the nature of presumptive interdigitating cells of the thymus of an ectothermic vertebrate, the turtle Mauremys caspica. This model is specially useful because of the seasonal variations that affect the reptilian lymphoid organs. Immature pro-interdigitating cells and phagocytosing mature interdigitating cells are described with special emphasis on their ultrastructural characteristics and possible relationships with monocytes and macrophages.     

Electron-microscopic study of the development of the periarteriolar zone in splenic white pulp of rats

Summary To obtain more information concerning the origin of interdigitating cells, the postnatal development and morphology of the periarteriolar lymphatic sheath in splenic white pulp of rats was investigated by light- and electron-microscopy. Special attention was paid to the ontogeny of interdigitating cells. The spleens of the animals were studied in the age range from 1 h to 28 days after birth.The splenic white pulp of neonatal rats consists only of a few reticuloblasts, which are concentrically arranged around central arterioles. After 21 h an increase in promonocytes and monocytes was noted. Between the fifth and seventh postnatal day monocytogenic cells with a light and almost translucent cytoplasm appear, which display long cytoplasmic projections between the adjacent cells. Neighbouring lymphocytes often insert finger-like processes into the invaginated cellular membrane of these transitional forms. This intimate cellular contact is supported by zonulae occludentes. These cells represent transitional forms between monocytes and interdigitating cells.From seven days of age onwards typical interdigitating cells were present as in adult animals. After the differentiation into an inner and outer periarteriolar lymphatic sheath, the T-cell-dependent area of splenic white pulp has attained its adult appearance and further changes are not to be expected.On the basis of these findings, it is highly probable that interdigitating cells develop via transformation of monocytes.This investigation was supported by the Deutsche Forschungsgemeinschaft (^*He 537)     

The effect of the seasonal cycle on the splenic leukocyte functions in the turtle Mauremys caspica

The reptile immune system is strikingly affected by seasonal variations, which induce changes in the structure of the lymphoid organs and in the function of the leukocytes. The aim of this work is to study several functions of splenic leukocytes from the turtle Mauremys caspica along its seasonal cycle. The functions assayed were adherence to substrate, mobility directed to a chemoattractant gradient (chemotaxis), lymphoproliferative response to mitogens, antibody-dependent cellular cytotoxicity, and natural killer-like cell-mediated cytotoxicity. Splenic leukocytes showed a positive response in all the assays, and this response was similar to that of mammals. In regard to the effect of the seasonal cycle, we have observed in winter a low adherence to substratum and high chemotaxis and cytotoxic activity, whereas in spring, only lymphoproliferation induced by mitogens showed high values except with lipopolysaccharide, which did not induce any seasonal variation in proliferation percentages. In summer, a high chemotaxis and cytotoxicity were observed, while in autumn, adherence to substratum was increased, but chemotaxis, cytotoxicity, and proliferation were clearly diminished. Our results demonstrate that splenic leukocyte functions are affected by the seasonal cycle, which induces a different pattern of response depending on the function studied.     

In vitro proliferation of blood,spleen and thymus leukocytes from the turtle Mauremys caspica

Cell-mediated immune responses is commonly evaluated by cell proliferation assays. Mitogens are known to induce a vigorous proliferative response in lymphoid cells from mammals but relatively fewer studies have investigated mitogen-mediated lymphoproliferation in non-mammalian animals. In the present work, we incubated spleen, thymus and blood leukocytes with phytohaemagglutinin (PHA), concanavalin A (Con A), lipopolysaccharide (LPS) and pokeweed mitogen (PWM), by different times of incubation (96 and 120 h) and at different concentrations. Our results show that the optimal mitogen concentrations inducing proliferation on leukocytes from Mauremys caspica were 20 microg/ml PHA, 1 microg/ml Con A, 12.5 microg/ml LPS and 1/150 dilution PWM. The optimal time of incubation was dependent on the type of leukocytes (peripheral blood leukocytes, splenic leukocytes or thymic cells) and the mitogen utilized.     

The immune response of thymic cells from the turtle Mauremys caspica

In the present work several known mammalian leukocyte functions such as directed mobility, proliferative response to mitogens, antibody-dependent cellular cytotoxicity (ADCC) and natural killer (NK)-mediated cytotoxicity were studied in female and male Mauremys caspica turtles. Since the reptilian thymus shows seasonal variations in its structure, we have performed all the assays along the seasonal cycle. Our results show that thymic cells from M. caspica are able to migrate through a chemo-attractant gradient, to proliferate in response to the mitogens phytohaemagglutinin (PHA) and concanavalin A (Con A), and to kill tumoral target cells by both ADCC-mediated and NK-mediated cytotoxicity. Those functions were differentially affected by the seasonal cycle; in general, in autumn the functions studied showed the smallest values for both sexes, while in summer the highest values of cytotoxicity and chemotaxis were found in females. The proliferative responses to PHA and Con A were higher for both sexes in spring and for females in winter than in the other seasons. In summary, thymic cells from M. caspica show a wide range of immune functions, and these are modulated heterogeneously by the seasonal cycle in both sexes.     

Ventilatory responses to temperature variation in the fresh water turtle,Mauremys caspica leprosa

A study of lung gas exchange in the fresh water turtle Mauremys caspica leprosa at normal physiological body temperatures (15, 25 and 35 °C) was extended to extreme temperatures (5 and 40 °C) to determine whether the direct relationship between body temperature and ventilatory response found in many lung-breathing ectotherms including other chelonian species was maintained. From 5 to 35 °C the lung ventilation per unit of O₂ uptake and CO₂ removed declined with temperature. Consequently, lung CO₂ partial pressure increased with temperature. Its value was maintained within narrow limits at each thermal constant, suggesting a suitable control throughout the complete ventilatory cycle. At 40 °C the ventilatory response showed the opposite trend. The ratios of ventilation to lung gas exchange increased compared to their values at 35 °C. The impact of this increased breathing-lowering the estimated mean alveolar CO₂ partial pressure-was nevertheless less than expected due to an increase in calculated physiological dead space. This suggests that the relative hyperventilation in response to hyperthermia found in Mauremys caspica leprosa is related to evaporative heat loss.Abbreviations BTPS body temperature, ambient pressure, saturated with water vapour - CTM critical thermal maximum - F_N2 fractional concentration of nitrogen - PA _CO2or PL _CO2 alveolar or lung CO₂ pressure - PA_O2or PL_O2 alveolar or lung O₂ pressure - PI_O2 inspired O₂ pressure - R respiratory exchange ratio - STPD standard temperature, standard pressure, dry - T _a ambient temperature - T _b body temperature - VA alveolar ventilation - VA/VCO₂ relative alveolar ventilation (alveolar ventilation per unit of CO₂ removed) - VO₂ O₂ uptake - VCO₂ CO₂ output - V _D anatomical dead space volume - V _D physiological dead space volume - VE/VO₂ ventilatory equivalent for O₂ - VE pulmonary ventilation or expiratory minute volume - VE/VCO₂ ventilatory equivalent for CO₂ - V _T tidal volume     

Interdigitating cells in the white pulp of the human spleen

Summary Interdigitating cells are demonstrated as a special type of fixed cell in the periarteriolar lymphocytic sheaths of the human spleen. These cells show typical ultrastructural features as well as a characteristic enzyme histochemical pattern that distinguish them from other reticular cells in the splenic white pulp.     

Ultrastructure of the jugular body of Rana pipiens

Summary The jugular bodies in adult Rana pipiens, are surrounded by a capsule of mesothelium and connective tissue, and their parenchyma consists of cell cords arranged in a sinusoidal network. The cell cords are formed by irregular reticular cells, showing numerous filaments and joined together by zonulae adhaerents. The intercellular spaces are filled by reticular fibres and free cells. These latter are small and medium lymphocytes, lymphoblasts, and developing and mature plasma cells. Additionally, free macrophages, neutrophils and acidophils also occur. Sinusoidal blood vessels show thin walls with numerous filaments and pinocytotic vesicles. They exhibit a discontinuous basement membrane, and tight junctions frequently occur between endothelial cells. Occasionally, lymphatic vessels are found and the innervation is principally vasomotor, although nerve endings appear remarkably near reticular cells and lymphocytes. The jugular bodies of adult R. pipiens are plasma cell and antibody-forming organs, whose functional significance is discussed in relation to their ultrastructural organization.     

Ultrastructural changes in the thymus of the turtle Mauremys caspica in relation to the seasonal cycle

Summary Changes in the ultrastructure of the thymus of the turtle Mauremys caspica, with special reference to its non-lymphoid components, were studied in relation to the seasonal cycle. The thymic cortex contains framework-forming epithelial-reticular cells and free macrophages, while the medulla includes, in addition, mature and presumptive pro-interdigitating cells. The ultrastructural features of these cells are generally similar to those described for non-lymphoid components of the mammalian thymus. The turtle thymus undergoes cortical involution in spring, with recovery periods in May–June and during autumn. A moderate involution occurs in winter. At the beginning of spring, cortical (but not medullary) epithelial-reticular cells show degenerative changes, probably related to high levels of circulating testosterone. In spring and autumn, mature interdigitating cells are absent, but macrophages, monocytes, and pro-interdigitating cells are found. During May–June, the cortical epithelial-reticular population recovers and macrophages, monocytes, and interdigitating cells are actively phagocytic. In summer, the epithelial-reticular cells in both cortex and medulla display normal ultrastructural features; mature and immature interdigitating cells are absent and some macrophages are detected occasionally. The results suggest that non-lymphoid components of the reptilian thymus can play a role in governing T-lymphocyte differentiation, and that the thymic cortex and medulla exhibit different cycles of seasonal activity.     

Specific localization of epidermal-type fatty acid binding protein in dendritic cells of splenic white pulp

Dendritic cells in the splenic white pulp of mice were intensely immunoreactive for epidermal-type fatty acid binding protein (E-FABP). This specific immunostaining revealed a clear difference in morphology between the dendritic cells in the periarterial lymphoid sheath (PALS) and follicular dendritic cells in the follicles in terms of cell sizes and process branching. No immunoreactivity was detected in dendritic cells in the marginal zones and the red pulp, although endothelial cells of almost all capillaries in the red pulp were immunoreactive for E-FABP. After peritoneal injection of lipopolysaccharide, the immunoreactive cells in PALS progressively enlarged and became rounded in shape with a peak in size at 24 h postinjection and they eventually resumed the dendritic form at 48 h postinjection. Within each of the enlarged immunoreactive cell perikarya were included small immunonegative apoptotic cells, presumptive lymphocytes. Taken together, E-FABP is useful as a marker for dendritic cells in the splenic white pulp, and may be involved through combination with fatty acids in antigen presentation and retention as well as in cytokine production.     

Immunocytochemical study of the hypothalamic magnocellular neurosecretory nuclei of the snake Natrix maura and the turtle Mauremys caspica

Summary An immunocytochemical study of the magnocellular neurosecretory nuclei was performed in the snake Natrix maura and the turtle Mauremys caspica by use of antisera against: (1) a mixture of both bovine neurophysins, (2) bovine oxytocin-neurophysin, (3) arginine vasotocin, and (4) mesotocin. Arginine vasotocin- and mesotocin-immunoreactivities were localized in individual neurons of the supraoptic and paraventricular nuclei, with a distinct pattern of distribution in both species. The same cells appeared to be stained by the anti-oxytocin-neurophysin and anti-mesotocin sera. The supraoptic nucleus can be subdivided into rostral medial and caudal portions. In N. maura, but not in M. caspica, neurophysin-immunoreactive neurons were found in the retrochiasmatic nucleus. No immunoreactive elements were seen in the suprachiasmatic nucleus of both species after the use of any of the antisera. A dorsolateral aggregation of neurophysin-containing cells, localized over the lateral forebrain bundle, was present in both species. Magnocellular and parvocellular neurophysin-immunoreactive neurons were present in the paraventricular nucleus of both species. In the turtle, the paraventricular neurons were arranged into four distinct layers parallel to the ependyma; these neurons were bipolar with the major axis perpendicular to the ventricle, and many of them projected processes toward the cerebrospinal-fluid compartment. In N. maura a group of large neurons of the paraventricular nucleus was found in a very lateral position. The posterior lobe of the hypophysis and the external zone of the median eminence contained arginine vasotocin- and mesotocin-immunoreactive nerve fibers. The lamina terminalis of both species was supplied with a dense bundle of fibers containing immunoreactive neurophysin. Neurophysin-immunore-active fibers were also present in the septum, some telencephalic regions, including the cortex and the olfactory tubercule, in the paraventricular organ, and the periventricular and periaqueductal gray of the brainstem.This work was partially supported by a Grant S-85-39 from the Direccion de Investigaciones, Universidad Austral de Chile to E.M. Rodriguez     

Apical membrane potentials and intracellular potassium and sodium activities in the gallbladder of the freshwater turtle Mauremys caspica

Open-tip and liquid ion-exchanger microelectrodes were used to measure transapical membrane potential (Va), fractional voltage ratio (fa) and intracellular sodium and potassium activities (aiNa, aiK) in Mauremys caspica gallbladder under open circuit conditions. The average values (+/- SEM) for Va and fa were -32 +/- 3 and 0.20 +/- 0.03 mV respectively. aiNa and aiK were, respectively, 17 +/- 4 and 82 +/- 7 mM. These results suggest that the mechanisms of Na+ and K+ transport in this tissue are essentially similar to those observed in leaky epithelia in general.     

中华鳖精子的超微结构

爬行纲在动物进化中占有重要地位,而且爬行纲动物种类繁多,生态环境和生活习性差异颇为明显。关于爬行动物生殖特性的资料很有限,而且由于动物种类的复杂性,不同动物的研究结果差异较大(Gustavo et al.,2004),缺乏统一的结构模式。精子的形态结构与动物的生殖特性直接相关,在一     

Ultrastructure of lymphatic capillaries in the human dental pulp

Summary Occlusal intradentinal cavities, prepared in normal human premolars and third molars to be extracted for orthodontic reasons, were filled for 7 to 11 days with gutta percha. A superficial pulpitis with localized small abscesses developed in the pulp chamber. Under local anesthesia, 0.2 to 0.3 cc of sterile colloidal carbon was injected in the pulp horn and the teeth were extracted 1 to 3 h later. Lymphatic capillaries could thus be identified in the pulpal tissues. They were characterized by a thin endothelium with occasional large intercellular clefts, absence or incompleteness of basement membrane, absence of pericytes, absence of luminal red blood cells, and presence of a filamentous material between the endothelium and the surrounding collagen fibrils. Moreover, some structural variations were observed.     

The three-dimensional structure of human splenic white pulp compartments.

The precise arrangement of B- and T-lymphocytes in the different compartments of the human splenic white pulp is still largely unknown. We therefore performed a 3D reconstruction of 150 serial sections of a representative adult human spleen alternately stained for CD3 and CD20. The results indicate that the T-cell regions of human spleens may be interrupted by B-cell follicles. Therefore, there is no continuous periarteriolar lymphatic T-cell sheath (PALS) around white pulp arterioles. An arteriole may be surrounded by T-lymphocytes at one level, then run across a follicle without any T-cells around, and finally re-enter a T-cell region. T- and B-cell compartments are intricately interdigitated in the human splenic white pulp. CD4(+) T-lymphocytes and the typical fibroblasts of the T-cell region may extend as a thin shell at the follicular surface within the marginal zone. On the other hand, IgD(++) B-cells continue from the follicular outer marginal zone along the surface of the T-cell region. Our findings indicate that the microanatomy of the splenic white pulp differs between humans and rodents. This may have consequences for the immigration of recirculating lymphocytes and for initial interactions among antigen-specific T- and B-lymphocytes.     

Synthesis of platelet-derived growth factor by cells of splenic red pulp in normal rats

A population of cells in the spleens of normal rats was found to contain platelet-derived growth factor (PDGF) B chain mRNA. These cells were found predominantly in the red pulp and nuclear morphology of some was consistent with that of macrophages. Similar cells were also shown by immunocytochemical staining to contain PDGF-AB/BB. These PDGF-positive cells were also found almost exclusively in the red pulp. It has been suggested by others that PDGF plays an important role in the function of the lymphohemopoietic microenvironment.     

Splenic white pulp as a thymus-independent area in the African clawed toad,Xenopus laevis

Summary An indirect immunofluorescence study of the frozen sections of the spleen of an anuran amphibian, Xenopus laevis, showed that lymphocytes bearing a small amount of immunoglobulin (Ig) were localized mostly in the white pulp of non-immunized toads. There were fewer fluorescent cells in the red pulp. In the toads hyperimmunized with human gamma globulin (HGG), cells with strong cytoplasmic fluorescence increased significantly in the outer part of the white pulp. Electron microscopy of spleens from these toads showed that plasma cells at different stages of maturation were abundant in the white pulp, whereas in the red pulp, a smaller number of maturer plasma cells were observed. These results indicate that, in contrast with its mammalian counterpart, the splenic white pulp of this anuran is the site where thymusin-dependent lymphocytes commence blast formation and transformation into plasma cells.     

Cytological structure of splenic white pulp in persons of different age

Spleens (27) obtained from human corpses (from 1 year up to 85 years) have been investigated. By means of morphometrical grid amount of cells in the periarterial lymphoid muffs (PLM) and in marginal zones (MZ) of the spleen have been counted. In both structures of the white pulp small lymphocytes make the greatest number. Middle lymphocytes in comparison to the small ones are 1.5-4 times less in most of the age groups investigated. Amount of plasma cells is small. The part of reticular cells is 21-46% in MZ and 20-36% in PLM from the total amount of cells. In PLM immediately around the artery tightly packed to each other small lymphocytes are situated. Among small lymphocytes reticular cells are situated. A similar arrangement of cells is kept along the whole thickness of PLM. In MZ distance between cells of the lymphoid line is a little greater than in PLM. To singularly situating reticular cells small and middle lymphocytes are immediate neighbours. Plasma cells, as a rule, occur seldom; either middle lymphocytes, or reticular cells adjoin them. Sometimes, in PLM and MZ macrophages occur; they are situated in the areas free from other cells.